The present invention relates to a servo pump suitable for use in machineries such as industrial robots, vibration beds and so forth.
To cope with the current demand for energy conservation, hydraulic systems having a variable-displacement type pump, referred to as a "servo pump," are becoming popular. In these systems the servo pump is used as a driving source for driving an actuator such as a hydraulic cylinder, hydraulic motor or the like. It is also preferred in these known hydraulic systems that the servo pump is situated as closely as possible to the actuator, in order to eliminate unfavourable effect which may be incurred through the piping system which interconnects the servo pump and the actuator.
In the conventional hydraulic systems, however, it is difficult to position the servo pump closely to the actuator, mainly because the size of the servo pump itself is to large.
Under this circumstance, attempts have been made to reduce the sizes of the pump and motor to realize a compact construction of the servo pump as a whole. As a matter of fact, however, there still is a practical limit in the reduction of the size and weight of the servo pump due to structural reasons.